11ASYNCHRONOUS PROGRAMMING
The central part of a computer, the part that carries out the individual steps that make up our programs, is called the processor. The programs we have seen so far are things that will keep the processor busy until they have finished their work. The speed at which something like a loop that manipulates numbers can be executed depends pretty much entirely on the speed of the processor.
But many programs interact with things outside of the processor. For example, they may communicate over a computer network or request data from the hard disk—which is a lot slower than getting it from memory.
When such a thing is happening, it would be a shame to let the processor sit idle—there might be some other work it could do in ...
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